221 research outputs found
Electronic structures of B-2p and C-2p of boron-doped diamond film by soft X-ray absorption and emission spectroscopy
X-ray absorption (XAS) and emission (XES) spectroscopy near B-K and C-K edges
have been performed on metallic (~1at%B, B-diamond) and semiconducting
(~0.1at%B and N, BN-diamond) doped-diamond films. Both B-K XAS and XES spectra
shows metallic partial density of state (PDOS) with the Fermi energy of 185.3
eV, and there is no apparent boron-concentration dependence in contrast to the
different electric property. In C-K XAS spectrum of B-diamond, the impurity
state ascribed to boron is clearly observed near the Fermi level. The Fermi
energy is found to be almost same with the top of the valence band of non-doped
diamond, E_V, 283.9 eV. C-K XAS of BN-diamond shows both the B-induced shallow
level and N-induced deep-and-broad levels as the in-gap states, in which the
shallow level is in good agreement with the activation energy (E_a=0.37 eV)
estimated from the temperature dependence of the conductivity, namely the
change in C-2p PDOS of impurity-induced metallization is directly observed. The
electric property of this diamond is mainly ascribed to the electronic
structure of C-2p near the Fermi level. The observed XES spectra are compared
with the DVX-alpha cluster calculation. The DVX-alpha result supports the
strong hybridization between B-2p and C-2p observed in XAS and XES spectra, and
suggests that the small amount of borons (<1at%) in diamond occupy the
substitutional site rather than interstitial site.Comment: submitted to Phys. Rev. B, 5 pages and 5 figure
Pressure-induced phase transition of Bi2Te3 into the bcc structure
The pressure-induced phase transition of bismuth telluride, Bi2Te3, has been
studied by synchrotron x-ray diffraction measurements at room temperature using
a diamond-anvil cell (DAC) with loading pressures up to 29.8 GPa. We found a
high-pressure body-centered cubic (bcc) phase in Bi2Te3 at 25.2 GPa, which is
denoted as phase IV, and this phase apperars above 14.5 GPa. Upon releasing the
pressure from 29.8 GPa, the diffraction pattern changes with pressure
hysteresis. The original rhombohedral phase is recovered at 2.43 GPa. The bcc
structure can explain the phase IV peaks. We assumed that the structural model
of phase IV is analogous to a substitutional binary alloy; the Bi and Te atoms
are distributed in the bcc-lattice sites with space group Im-3m. The results of
Rietveld analysis based on this model agree well with both the experimental
data and calculated results. Therefore, the structure of phase IV in Bi2Te3 can
be explained by a solid solution with a bcc lattice in the Bi-Te (60 atomic%
tellurium) binary system.Comment: 12 pages, 5 figure
Characterization of Linear Poly(N-isopropylacrylamide) and Cloud Points in its Aqueous Solutions
Catalytic ozone oxidation of benzene at low temperature over MnOx/Al-SBA-16 catalyst
The low-temperature catalytic ozone oxidation of benzene was investigated. In this study, Al-SBA-16 (Si/Al = 20) that has a three-dimensional cubic Im3m structure and a high specific surface area was used for catalytic ozone oxidation for the first time. Two different Mn precursors, i.e., Mn acetate and Mn nitrate, were used to synthesize Mn-impregnated Al-SBA-16 catalysts. The characteristics of these two catalysts were investigated by instrumental analyses using the Brunauer-Emmett-Teller method, X-ray diffraction, X-ray photoelectron spectroscopy, and temperature-programmed reduction. A higher catalytic activity was exhibited when Mn acetate was used as the Mn precursor, which is attributed to high Mn dispersion and a high degree of reduction of Mn oxides formed by Mn acetate than those formed by Mn nitrate
Solution Properties of 1,3-Cyclohexadiene Polymers by Laser Light Scattering and Small-Angle Neutron Scattering
Understanding Novel Superconductors with Ab Initio Calculations
This chapter gives an overview of the progress in the field of computational
superconductivity.
Following the MgB2 discovery (2001), there has been an impressive
acceleration in the development of methods based on Density Functional Theory
to compute the critical temperature and other physical properties of actual
superconductors from first-principles. State-of-the-art ab-initio methods have
reached predictive accuracy for conventional (phonon-mediated) superconductors,
and substantial progress is being made also for unconventional superconductors.
The aim of this chapter is to give an overview of the existing computational
methods for superconductivity, and present selected examples of material
discoveries that exemplify the main advancements.Comment: 38 pages, 10 figures, Contribution to Springer Handbook of Materials
Modellin
Successful application of ancient DNA extraction and library construction protocols to museum wet collection specimens
Millions of scientific specimens are housed in museum collections, a large part of which are fluid preserved. The use of formaldehyde as fixative and subsequent storage in ethanol is especially common in ichthyology and herpetology. This type of preservation damages DNA and reduces the chance of successful retrieval of genetic data. We applied ancient DNA extraction and single stranded library construction protocols to a variety of vertebrate samples obtained from wet collections and of different ages. Our results show that almost all samples tested yielded endogenous DNA. Archival DNA extraction was successful across different tissue types as well as using small amounts of tissue. Conversion of archival DNA fragments into single-stranded libraries resulted in usable data even for samples with initially undetectable DNA amounts. Subsequent target capture approaches for mitochondrial DNA using homemade baits on a subset of 30 samples resulted in almost complete mitochondrial genome sequences in several instances. Thus, application of ancient DNA methodology makes wet collection specimens, including type material as well as rare, old or extinct species, accessible for genetic and genomic analyses. Our results, accompanied by detailed step-by-step protocols, are a large step forward to open the DNA archive of museum wet collections for scientific studies
Modified carbon-containing electrodes in stripping voltammetry of metals. Part II. Composite and microelectrodes
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